MICROBIO: LAB
PROKARYOTES
Characteristics/ Processes of Life
GROWTH – an increase in size
REPRODUCTION – an increase in number
RESPONSIVENESS – an ability to react to environmental stimuli
METABOLISM – controlled chemical reactions
CELLULAR STUCTURE – membrane-bound structure capable of ALL of the above
functions
External Structure of Prokaryotic Cell
GLYCOCALYSES (GLYOCALYX)
o Gelatinous, sticky substance that surrounds the outside of the cell
o CAPSULE – when the glycocalyx of a prokaryote is firmly attached to the cell
surface
o SLIME LAYER – when it is loose and water soluble
o Functions:
Both types protect the cell from desiccation
Both increase the cell’s ability to cause disease
Capsules – protect cells from phagocytosis
Slime layers – enable cells to adhere to each other and to environmental
surfaces
FLAGELLA
o Responsible for cell motility; long, whip like extensions from the cell surface and
glycocalyx that propel a cell through its environment
o Composed of a filament, a hook and basal body
*** Filament – the whip like shaft that extends into the cell’s environment;
composed of FLAGELLIN (a CHON)
o Arrangement:
Monotrichous – single flagellum
Lophotrichous – grouped at one end of the cell
Amphitrichous – grouped at both ends of the cell
Peritrichous – cover the surface of the cell
RVF
o ENDOFLAGELLA – special flagella of spirochetes that spiral tightly around the
cell instead of protruding into the environment
FIMBRIAE
o Short, sticky, proteinaceous, nonmotile extensions of some bacteria that help cells
adhere to one another to substances in the environment
o They have an important function in BIOFILMS – slimy masses of bacteria
adhering to a substrate/surface by means of fimbriae and glycocalyces
o PILI – hollow nonmotile tubes of CHON called PILIN
They join2 bacteria cells and mediate the movement of DNA from one cell to
another – CONJUGATION.
Prokaryotic Cell Walls
Provides structure and shape to the cell and protects it from osmotic forces
Assists some cells in attaching to other cells or in eluding antimicrobial drugs
Bacterial Cell Walls
Composed of PEPTIDOGLYCAN – complex polysaccharide; composed of 2 regularly
alternating sugars, N-acetyglucosamine (NGA) and N-acetylmuramic acid (NAM)
Gram (+) Cells
o Have relatively thick layer of peptidoglycan; with teichoic acids
o Thick cell wall retains the crystal violet dye used in Gram staining
Gram (-) Cells
o Have only a thin layer of peptidoglycan
o Also have an outside membrane composed of phospholipids, porins (channel
proteins) and lipopolysaccharide (LPS)
o LPS – lipid portion is well known as LIPID A (Endotoxin)
o LIPID A – released from dead cells (infection with G-cells) when the cell wall
disintegrates and it may trigger fever, vasodilation, inflammation, shock and blood
clotting in humans
Morphology of Prokaryotic Cells
4 Major Shapes
o Cocci – spherical
o Bacilli – rods, short bacilli – coccobacilli
o Spiral Forms – comma-shaped, s-shaped or spiral shaped
o Pleomorphic – lacks of distinct shape
RVF
Reproduction of Prokaryotic Cells
ALL reproduce asexually
o BINARY FISSION – parenteral cell disappears with the formation of 2 daughter
cells
o SNAPPING DIVISION – the parent’s outer wall tears apart with a snapping
movement to create the daughter cells
o BUDDING – an outgrowth of the original cell receives a copy of DNA, enlarges and
is taken out of the parent cell
RVF
